A medical surveillance program for persons potentially exposed to polychlorobiphenyls (PCBs), dibenzo-p-dioxins (PCDDs), and dibenzofurans (PCDFs) from an electrical transformer fire was described. A total of 482 individuals, 84 percent male, potentially exposed to PCBs, PCDDs, and PCDFs from an electrical transformer fire in a Binghamton, New York, office building in 1981 participated in the program. During the fire, about 180 gallons of a dielectric fluid containing 65 percent Aroclor-1254 (11097691) leaked from a transformer. Serum PCB concentrations were determined immediately after and 9 to 12 months (mo) following the fire. A blood screen for 20 biochemical parameters was performed 9 to 12mo after the fire. A total of 450 subjects were interviewed 6 to 12mo after the fire to obtain information about the nature and extent of exposure and sociodemographic characteristics. A total of 147 firemen and other persons who were in the building for 25 hours or more were questioned about symptoms and examined for physical abnormalities after the fire. Mean serum PCB concentrations determined initially and at followup were 6.90 and 6.50 parts per billion, respectively. The mean serum PCB concentrations were positively correlated with extent of reported exposure. Serum PCB concentrations were also significantly correlated with liver enzyme and lipid concentrations; however, initial and followup liver enzyme and lipid concentrations were not significantly correlated with extent of exposure after covariance adjustment. About 50 percent of the subjects examined had skin lesions; however, no cases of chloracne were seen. Of five participants who reported hepatitis or liver problems, four admitted to heavy drinking. The authors conclude that exposure to contaminants from the building did not cause any significant absorption of PCBs or any major short term health effects.